Labels using pressure sensitive adhesives are well known. In general, pressure sensitive labels involve the label itself, a pressure sensitive adhesive, and a backing sheet upon which the label or labels are mounted. The backing sheet is usually coated with a release coating such as a silicone so that the adhesive coated labels may be more easily removed. Various types of adhesives may be used to coat the labels. For example, the adhesives may be permanent or removable. The nature of the adhesive, whether permanent or removable, is often specified by the force required to peel (peel force) a one-inch wide sample strip at right angles from a stainless steel surface to which it has been adhered. The designation "permanent adhesive" is normally applied to adhesives having a peel force in the order of 3 pounds or more, while pressure sensitive adhesives having a peel force of less than about two pounds are normally referred to as removable adhesive coatings.
Most modern pressure-sensitive adhesives are applied to the substrate or label stock by one of three techniques: (1) coating from an organic solvent based solution, (2) coating from a suspension or dispersion such as an aqueous latex, or (3) coating or extruding a hot melt pressure-sensitive composition.
Reference is made to U.S. Pat. No. 4,543,099, granted Sep. 24, 1985, and to U.S. Pat. No. 4,693,772, granted Sep. 15, 1987, as disclosing prior art relating to pressure sensitive adhesives and to a sealant, respectively.
Hot melt adhesives have certain significant advantages over adhesives applied in other ways, and for adhesives where it is desirable to have resistance to ultraviolet light and to plasticizers (which may soften or degrade the adhesive), hot melt adhesives using acrylic material are often used. However, acrylic hot melt adhesives are moderately expensive.
Accordingly, an important object of the invention is to provide a high quality, pressure sensitive adhesive which is less expensive than known pressure sensitive, high quality adhesives.